I didn't have to remove any live roots to get the tree into position! I did remove a few dead roots and old growing media that had decayed into black goo.

The first pic is the originally planned "front" of tree and rock. However, after planting the tree onto the rock, I also like the "back" (second pic) as much if not better than the "front". There is a better root flare on the "back" of the tree.

These close-up pics show extra rocks (red arrows) I added to the top of the growing media which adds more of a natural feel to the composition as if the tree is actually growing on a mountain ledge. (1st pic original front and 2nd pic is the back.) I'm not sure yet whether I'll leave the added rocks to show the tree. If I do leave the extra rocks I'll plant moss in the gaps.

I also am pondering adding a few tiny perennial plants further out from the tree so the scene is not quite as stark. "Tiny" perennials with small foliage/flowers so that the proper scale is preserved.

This tree was nursery-grown in peat-based growing media so the media had decayed into a black organic goo. I rinsed the roots out so that this goo would not cause root rot when I potted it up into my porous bonsai media. This tree responded very well to this treatment. (not recommeded for pines by the pine experts but I've rinsed roots with a water jet for deciduous trees, Taxus, and Junipers with no ill effects)